A filter element may include a hollow cylindrical filter pack, where a filter pack may be defined as any structure that includes a filter medium. The interior of the filter pack may be supported by an internal core and the exterior of the filter pack may be supported by an external cage. One or both ends of the filter pack are typically bonded to a closure such as an end cap. The end of the filter pack may be bonded to the end cap by any suitable technique which provides sufficient filter integrity, including melt bonding or the use of a potting material, such as an epoxy, a urethane, or a hot melt adhesive.
When a filter pack is bonded to an end cap, an end portion of the end cap may be liquefied, for example, by heating it until the end portion melts, and the filter pack may be inserted into the molten portion. Alternatively, a liquid potting material may be applied to the end cap and the end of the filter pack may be inserted into the potting material. The liquid bonding material, e.g., other the molten portion of the end cap or the potting material, then solidifies or hardens, forming a bond between the filter pack and the end cap.
In a typical melt bonding and/or potting material bonding, the end of the core and/or the end of the cage may be inserted into the liquid bonding material along with the end of the filter pack. Unfortunately, the end of the core and/or cage then displaces a significant amount of the liquid bonding material. This displaced bonding material may be forced into the bonding area between the end cap and the end of the filter pack, resulting in excess bonding material. The excess bonding material may cause improper bonding and compromise the integrity of the bond between the end cap and the end of the filter pack. The excess bonding material may also be drawn deep into the end of the filter pack, where it may damage or blind the filter medium or bond the filter pack to the core.
The liquid bonding material displaced by the end of the core and/or cage may also be forced onto the outer or inner surfaces of the filter element, where it can resolidify as globules or ridges. Not only are these globules or ridges unsightly; they can also interfere with the fit of the filter element into a housing and with the flow of fluid around and through the filter element.
Another problem with conventional cylindrical filter elements is that pressures exerted on the filter pack at the bond during filtration and backwashing or blowback stress the bond between the filter pack and the end cap. Expansion or contraction of the filter pack due to the effects of temperature and/or moisture can also stress the bond between the filter pack and the end cap. Repeated stress on the bond may cause the bond to fail, allowing unfiltered fluid to bypass the filter pack and contaminate fluid that has been treated by the filter element.
One aspect of the present invention provides a filter element which comprises a hollow filter, a core disposed in the filter, and an end cap. The filter has a first end portion which includes an inner periphery and an inner diameter. The core has a first end portion including a first end and an outer wall structure. The outer wall structure has an outer diameter at the first end of the core corresponding to the inner diameter of the filter. The Core also has a recess at its end. The end cap is bonded to the filter at the first end portion of the filter. Solidified bonding material is disposed in the recess of the core, and the inner periphery of the filter is supported by the outer wall structure of the core near the bond.
Another aspect of the present invention provides a filter element which comprises a hollow filter, a core disposed in the filter, and an end cap. The filter has a first end portion which includes an inner periphery and an inner diameter. The core has first end portion including a first end and an outer wall structure. The outer wall structure has outer diameter corresponding to the inner diameter of the filter. The core also has a recess and an interlock arrangement at its first end. The end cap is bonded to the filter at the first end portion of the filter. Solidified bonding material is disposed in the recess of the core and faces or contacts the interlock arrangement of the core. The inner periphery of the filter is supported by the outer wall structure of the core near the bond.
Another aspect of the present invention provides a filter element which comprises a hollow filter, a core disposed in the filter, and an end cap. The filter has a first end portion, an inner periphery, and an inner diameter. The core has a first end portion including an outer wall structure having outer diameter corresponding to the inner diameter of the filter. The core also has a recess at its first end. The end cap is bonded to the filter at the first end portion of the filter, but the core is not bonded to the end cap. Solidified bonding material is disposed in the recess of the core, and the inner periphery of the filter is supported by the outer wall structure of the core near the bond.
Another aspect of the present invention provides a filter element comprising a hollow filter, a core disposed in the filter, and an end cap. The filter has a first end portion, an inner periphery, and an inner diameter. The core has a first end portion which includes an inner wall structure, an outer wall structure having an outer diameter corresponding to the inner diameter of the filter, and a base which intersects the inner surface of the outer wall structure and the outer surface of the inner wall structure. The core also has a recess at the first end of the core and the recess comprises a groove between the inner wall structure, the outer wall structure, and the base. The end cap is bonded to the filter at the first portion of the filter. Solidified bonding material is disposed in the recess of the core, and the inner periphery of the filter is supported by the outer wall structure near the bond.
Another aspect of the invention provides a filter element which comprising a hollow filter, a core, and an end cap. The filter has a first end portion and an inner periphery, and the core is disposed along the inner periphery of the filter. The core has a first end portion which includes an end face, an outer wall, an inner wall, and a recess. The recess is defined between the outer and inner walls and opens at the end face of the core. The end cap is bonded to the filter at the first end portion of the filter at the first end portion of the filter, and solidified bonding material is disposed in the recess of the core.
Filter elements embodying the present invention may be made by a method which comprise bonding an end cap to a first end portion of a filter, including solidifying bonding material in a recess of a core. The method also comprises supporting an inner periphery of the filter by an outer wall structure of the core near the bond. Filter elements embodying the present invention may be made by a method which comprises bonding an end cap to a first end portion of a filter, including solidifying bonding material in contact with or facing an interlock arrangement at a first end portion of a core. The method also comprises supporting an inner periphery of the filter with an outer wall structure of the core near the bond.
The embodiments of the invention represent a considerable advance in the state of the art. A filter element or a method which provides for supporting the periphery of a filter by a wall structure of a core at the bond and solidifying bonding material in a recess or in contact with an interlock arrangement provides for several advantages over the prior art. For example, when the end of a filter pack and the end of the core are inserted into the melted region of an end cap or a potting material in an end cap, excess bonding material displaced by the end of the core is not forced into the bonding area nor onto the inner or outer surfaces of the filter element. Rather, the displaced bonding material is contained in the recess and/or around the interlock arrangement of the core, enhancing the integrity if the bond and the effectiveness of the filter element.
In addition, because the filter pack is supported by the outer wall structure of the core at the bond, less stress is placed on the bond between the filter pack and the end cap. Thus, the likelihood of stress failure at the bond and the opportunity for untreated process fluid to leak through a failed bond and contaminate treated fluid are virtually eliminated.